The present invention relates to a fin material used for an automobile radiator.
The automobile radiator is used to prevent an excess rise in the temperature of the automobile engine section and cools the engine section by circulating the cooling medium such as water between the engine section and the radiator and radiating heat of water rised in temperature in the engine section. The radiator consists of a tube to pass water through and a fin to emit heat from the tube and is usually mounted on the front of the automobile. The airflow required to remove the heat from the radiator is supplied by an engine-drive fan to promote radiation of the heat.
As such a fin material for the radiator, a thin sheet made of a Cu-Sn alloy or Cu-Cd alloy has been utilized heretofore. This alloy is the material of which heat-resistance has been improved by adding a suitable amount of tin or cadmium into copper in the range unimpairing the excellent thermal conductivity and workability of copper so as to prevent the softening of the fin in a process for soldering the fin to a tube upon assembling the radiator. However, with the worsening of automobile travelling environment in recent years, it has become apparent that the conventional copper alloys are significantly inferior in corrosion resistance. In this corrosion the oxidized films of cuprous oxide are formed in layers on the surface on the fin and scale off to fall to pieces. According to circumstances it is feared that the corrosion proceeds in about two years after commencement of use and brings about falling off the fin from the tube.
For such a problem, the present inventors et al. have proposed a copper-lead alloy consisting of a small amount of lead as a material for the radiator fin excellent in corrosion resistance (refer to Japanese Patent Laid Open No. 207138/83). However, this Cu-Pb alloy has a disadvantage that with an increase in an additional amount of lead the embrittlement of the alloy is observed upon hot-working thereof thereby rendering it difficult.
Therefore, considering the workability of such alloy, the heat resistance of this alloy will be impaired.